For a vehicle, a valve stem seal assembly cooperates with a reciprocating valve stem shaft to provide lubrication and contain engine gases within engine inlet and exhaust ports (not shown). To accomplish these functions, the valve stem seal assembly typically includes an elastomeric seal with an attached metal retainer that is installed over a metal valve guide.
Such a valve stem seal assembly takes advantage of an elastomeric-to-metal seal between the elastomeric seal and the valve guide or a metal-to-metal grip between the retainer and the valve guide.
FIG. 1 illustrates a prior art side seal valve stem assembly 10. An elastomeric seal 12, with a garter spring 14 disposed thereon, are utilized to seal a valve stem shaft 16 of the valve stem assembly 10. A retainer 18, which is disposed within and on an outer surface 20 of the elastomeric seal 12, cooperates with the elastomeric seal 12, to seal a valve guide 22 at a single elastomeric-to-metal seal area 24.
FIG. 2 illustrates a prior art top seal valve stem assembly 30. An elastomeric seal 32, with a retainer 34 disposed thereto, are utilized to seal the valve stem shaft 36 at the top of the valve stem assembly 30. The retainer 34, in this case, is utilized to directly grip a valve guide 38 at a single metal-to-metal grip area 26.
Lately, however, manufacturers are requiring engines to have higher pressures within their inlet and exhaust ports. As a result, valve stem seals, like those in FIGS. 1 and 2, are being exposed to increased lifting forces, which in turn require the seals 12, 32 to resist being pushed off of the valve guides 22, 38 by these forces. As a result of these recent developments, past valve stem seals are not capable of sustaining the increased lifting forces. In many cases, because of its elastomeric characteristics, the elastomeric seal material fails to retain the seal, which results in loss of lubrication control and engine gases escaping through the valve stem and guide interface (not shown).
In response, elastomeric seal manufacturers are increasing the seal to guide interference of the elastomeric material. Unfortunately, increasing the seal to guide interference of the elastomeric seal then requires the seal to be installed with a greater installation load (i.e., force) which quite often results in over-installing the elastomeric seal or cutting the elastomer during initial installation or during cylinder head servicing. In either of these cases, the valve stem seal assembly fails to function properly.
With the increased pressures within the inlet and exhaust ports and the over-installation of the elastomeric seal in mind, what is sought is to take advantage of the increased seal ability of the elastomeric seal while further taking advantage of the metal grip ability of the retainer. By utilizing these advantages, a means to overcome the over-installation of the elastomeric seal is also sought.